1. Field of the Invention
The present invention relates to a vibrating gyroscope and a self-diagnosis method for a vibrating gyroscope.
2. Description of the Related Art
A vibrating gyroscope, which is used in a safety system for controlling the attitude of a vehicle or detecting when the vehicle rolls over, a car navigation system, and other apparatuses, is required to self-diagnose malfunctions. Known devices for performing the self-diagnosis function are disclosed, for example, in Japanese Unexamined Patent Application Publication Nos. 3-159877, 4-215017, 5-133755, 6-58760, 6-207946, 9-281138, 11-51655, and 2000-2542.
The known self-diagnosis methods include (1) monitoring a driving signal and a differential output signal of a vibrator and detecting a malfunction when the level of the signals exceeds a predetermined range, and (2) monitoring an output signal by applying a signal synchronized with a synchronous-detection signal between a differential circuit and a synchronous-detection circuit and detecting a malfunction when the value of the output signal exceeds a predetermined range.
In the first method described above, however, although the vibrating gyroscope can self-diagnose whether or not a malfunction has occurred, the vibrating gyroscope cannot detect the cause of the malfunction.
In the second method described above, the signal synchronized with the synchronous-detection signal is applied after the differential circuit and thus, a malfunction in a circuit after the position to which the signal is applied can be diagnosed. However, a malfunction in the vibrator itself, for example, a short circuit or opening of a plurality of detection electrodes of the vibrator cannot be diagnosed. In addition, since this method needs many circuits and large circuits, problems with the cost and reliability result.
In order to overcome the problems described above, preferred embodiments of the present invention provide a vibrating gyroscope, which is able to self-diagnose a malfunction in a vibrator and the peripheral circuits with low-cost and greatly increased reliability, an electronic device including such a novel vibrating gyroscope, and a self-diagnosis method for a vibrating gyroscope.
According to a first preferred embodiment of the present invention, the vibrating gyroscope includes a vibrator having a plurality of detection electrodes and vibrating in response to a driving signal and an applied angular velocity, a vibrator driving unit for applying a driving signal to the vibrator, a plurality of detection load-impedance elements connected to the plurality of detection electrodes for converting charges generated in the plurality of detection electrodes due to the vibration of the vibrator to voltage signals, a Coriolis-force detecting unit for outputting a Coriolis signal corresponding to the angular velocity based on the plurality of voltage signals, and an impedance changing unit for changing the impedance of at least one of the plurality of detection load-impedance elements.
The vibrating gyroscope may further include a self-diagnosis unit for performing self-diagnosis based on the variation in the Coriolis signal caused by changing the impedance of at least one of the plurality of detection load-impedance elements.
Preferably, in the vibrating gyroscope, the self-diagnosis unit performs self-diagnosis based on a transient characteristic of the Coriolis signal caused by changing the impedance of at least one of the plurality of detection load-impedance elements.
Also, each of the detection load-impedance elements may be a resistor or other suitable component.
According to a second preferred embodiment of the present invention, a self-diagnosis method for a vibrating gyroscope including a vibrator having a plurality of detection electrodes and vibrating in response to a driving signal and an applied angular velocity, a vibrator driving unit for applying a driving signal to the vibrator, a plurality of detection load-impedance elements for converting charges generated in the plurality of detection electrodes due to the vibration of the vibrator to voltage signals, and a Coriolis-force detecting unit for outputting a Coriolis signal corresponding to the angular velocity based on the plurality of voltage signals, the method including the step of performing self-diagnosis based on the variation in the Coriolis signal caused by changing the impedance of at least one of the plurality of detection load-impedance elements.
In the method of the present preferred embodiment of the present invention, preferably, the self-diagnosis is performed based on a transient characteristic of the Coriolis signal caused by changing the impedance of at least one of the plurality of detection load-impedance elements.
Also, each of the detection load-impedance elements may be a resistor or other suitable component.
With the features described above, in the vibrating gyroscope and the self-diagnosis method according to various preferred embodiments of the present invention, malfunctions of the vibrator and the peripheral circuits can be self-diagnosed.
In addition, according to another preferred embodiment of the present invention, a much more reliable electronic device can be provided.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.